Chemical Energetics Practice Questions
IGCSE (Cambridge) · IGCSE Chemistry · 146 free MCQs with instant results and detailed explanations.
146
Total
48
Easy
72
Medium
26
Hard
Start Practicing Chemical Energetics
Take a timed quiz or customize your practice session
Sample Questions from Chemical Energetics
Here are 10 sample questions. Start a quiz to get randomized questions with scoring.
Q1
Easy
What is the term used to describe the heat energy absorbed or released during a chemical reaction?
A.
Enthalpy
B.
Entropy
C.
Activation Energy
D.
Gibbs Free Energy
Show Answer & Explanation
Correct Answer: A
Enthalpy is a measure of the total heat content in a system and is specifically used to quantify the heat absorbed or released during a chemical reaction.
Q2
Easy
During an exothermic reaction, which of the following statements is true?
A.
Energy is absorbed by the system.
B.
The surroundings become colder.
C.
Energy is released to the surroundings.
D.
The reaction requires a catalyst.
Show Answer & Explanation
Correct Answer: C
In an exothermic reaction, energy is released to the surroundings, which typically results in an increase in temperature of the surroundings.
Q3
Easy
If 100 joules of energy is required to break the bonds in a reaction, and 150 joules is released when new bonds are formed, what is the overall energy change for the reaction?
A.
50 joules absorbed
B.
50 joules released
C.
100 joules absorbed
D.
100 joules released
Show Answer & Explanation
Correct Answer: B
The overall energy change is calculated by subtracting the energy required to break bonds from the energy released in forming new bonds: 150 joules - 100 joules = 50 joules released.
Q4
Medium
Which of the following statements best describes an exothermic reaction?
A.
It absorbs energy from the surroundings.
B.
It releases energy to the surroundings.
C.
It requires a catalyst to occur.
D.
It occurs only in gaseous states.
Show Answer & Explanation
Correct Answer: B
An exothermic reaction is characterized by the release of energy, typically in the form of heat, to the surroundings, making option B the correct answer.
Q5
Medium
In a calorimetry experiment, 50 g of water is heated from 20 °C to 80 °C. If the specific heat capacity of water is 4.18 J/g°C, how much energy is absorbed by the water?
A.
1250 J
B.
1240 J
C.
1350 J
D.
1400 J
Show Answer & Explanation
Correct Answer: B
Energy absorbed can be calculated using the formula Q = mcΔT. Here, m = 50 g, c = 4.18 J/g°C, and ΔT = 80 - 20 = 60 °C. Thus, Q = 50 * 4.18 * 60 = 1240 J.
Q6
Medium
What is the enthalpy change for the reaction: A + B → C + D, if the bond energies are: A-B = 400 kJ/mol, C-D = 300 kJ/mol, A-C = 250 kJ/mol, and B-D = 350 kJ/mol?
A.
-450 kJ/mol
B.
-320 kJ/mol
C.
150 kJ/mol
D.
320 kJ/mol
Show Answer & Explanation
Correct Answer: B
The enthalpy change can be calculated as the total bond energy of reactants minus that of products. Here, it results in a negative value of -320 kJ/mol, indicating an exothermic process.
Q7
Medium
When 100 g of magnesium burns in excess oxygen, it produces magnesium oxide. If the enthalpy change for the reaction is -600 kJ, how much energy is released when 50 g of magnesium burns?
A.
300 kJ
B.
600 kJ
C.
150 kJ
D.
200 kJ
Show Answer & Explanation
Correct Answer: A
The enthalpy change of -600 kJ corresponds to 100 g of magnesium. Therefore, for 50 g (half the mass), the energy released will be half of -600 kJ, which is 300 kJ.
Q8
Hard
A 2.0 g sample of a substance is burned in a calorimeter, raising the temperature of the water by 15 °C. If the specific heat capacity of water is 4.18 J/g°C, how much energy was released during the combustion?
A.
126.6 J
B.
125.4 J
C.
89.4 J
D.
62.5 J
Show Answer & Explanation
Correct Answer: A
The energy released can be calculated using the formula Q = m × c × ΔT, where m is the mass of water, c is the specific heat capacity of water, and ΔT is the change in temperature. Here, Q = 2.0 g × 4.18 J/g°C × 15 °C = 126.6 J.
Q9
Hard
During a reaction, the enthalpy change (ΔH) is -150 kJ/mol. If the reaction produces 0.5 moles of product, what is the total energy change in the reaction?
A.
-75 kJ
B.
75 kJ
C.
-300 kJ
D.
150 kJ
Show Answer & Explanation
Correct Answer: A
The total energy change can be found by multiplying the enthalpy change per mole by the number of moles produced. Here, ΔH = -150 kJ/mol and for 0.5 moles, total energy change = -150 kJ/mol × 0.5 mol = -75 kJ.
Q10
Hard
In an endothermic reaction, which of the following statements is true regarding the enthalpy change (ΔH)?
A.
ΔH is positive, indicating heat is absorbed.
B.
ΔH is negative, indicating heat is released.
C.
ΔH is zero, indicating no heat change.
D.
ΔH can be either positive or negative depending on the reaction.
Show Answer & Explanation
Correct Answer: A
In an endothermic reaction, the system absorbs heat from the surroundings, resulting in a positive enthalpy change (ΔH). This indicates that energy is required for the reaction to proceed, which is characteristic of endothermic processes.
Showing 10 of 146 questions. Start a quiz to practice all questions with scoring and timer.
Practice All 146 Questions →Other IGCSE (Cambridge) Subjects
Chemical Energetics — IGCSE (Cambridge) IGCSE Chemistry Practice Questions Online
This page contains 146 practice MCQs for the chapter Chemical Energetics in IGCSE (Cambridge) IGCSE Chemistry. The questions are organized by difficulty — 48 easy, 72 medium, 26 hard — so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.